1. Field of the Invention
The present invention relates to a load switch, and ore particularly to an improved multi-position automatic switching actuator for a load switch which makes it possible to appropriately switch one contact point to another and carry out a 3-position (open-close-earth) switch control and multi-position switch control by employing a single actuator.
2. Description of Related Art
In general, a load switch employs a power distribution system. The power distribution system includes an overhead power distribution line and a subterranean power distribution line, and allows electrical power supplied from a first substation to provide power to power receiving devices for power consumers. Such a load switch may be used to partition and branch power lines for the subterranean power lines.
As shown in FIG. 1, the load switch according to the conventional art includes a main body 1, four switching actuators 100 respectively disposed at upper portions of the main body 1 for making a movable contact move, and a plurality of three-phase main bushes 2 positioned at lower portions of the switching actuators 100 for receiving power from a first substation and selectively supplying or interrupting power to power receiving facilities of respective electric loads under the control of the switching actuators 100.
In a conventional load switch, the switching actuator 100 actuates respective movable contacts for the power received from one of the main bushes 2 depending upon its demand, thereby either supplying the power to another of the main bushes 2 or to respective power consumers, or interrupting the power supply.
The switching actuator for the conventional load switch will now be described.
As shown in FIGS. 2 and 5B, the switching actuator for the conventional load switch, known as a toggle-type control device, carries out a two-position contact switching. The switching actuator includes: a base plate 120; a driving shaft unit 130 disposed at a central portion behind the base plate 120 and having a driving shaft 132 protrudingly formed from a marginal end surface thereof; a subordinate driving shaft link unit 140 having a through hole 142 formed through an end portion thereof through which the driving shaft 132 extends so as to be coupled with the driving shaft unit 130; a spring 150 having a left end portion 151 hooked on a hook protrusion 134 extending backwardly from another end portion of the driving shaft unit 130, and another end portion 152 hooked on a protrusion 144 extending from an end portion of the subordinate driving shaft link unit 140; a central shaft unit 160 disposed below a portion at which the driving shaft unit 130 and the subordinate driving shaft link unit 140 are coupled with each other, and an end portion of which is movably engaged to a link 143; and a control handle 110 disposed at a front portion of the base plate 120 and having an insertion protrusion (not shown) formed at a center so as to be engaged to the driving shaft 132.
The base plate 120 includes a through hole (not shown) formed in a center thereof, and arc openings 121 for controlling a rotation of the driving shaft 132 are formed at left and right sides of the through hole (not shown).
As shown in FIGS. 4A and 4B, the driving shaft unit 130 includes: a stable arm 131; the driving shaft 132 extending from an end portion of the stable arm 131, wherein an insertion opening (not shown) is formed in an end portion of the driving-shaft 132 so that the control handle 110 is engaged in the insertion opening (not shown); a limit protrusion 133 protruding from the stable arm 131 to limit the rotation of the driving shaft unit 130; and the hook protrusion 134 extending from an end portion of the stable arm 131 so as to rotate in correspondence to the rotation of the driving shaft 132.
In the above constituted driving shaft unit 130, the hook protrusion 134 is hooked on the one end portion 151 of the spring 150, and the limit protrusion 133 is inserted into the arc opening 121 formed in the base plate 120, so that the rotation of the driving shaft unit 130 is limited accordingly.
As shown in FIGS. 5A and 5B, the subordinate driving shaft link unit 140 includes: a pair of stable pads 141; the link 143 provided between the pair of stable pads 141; the through hole 142 formed at the end of the stable pads 141 and having the driving shaft 132 extending therethrough; the hook protrusion 144 extending from another end portion of the stable pads 141 and being moved by the elasticity of the spring 150; and a limit protrusion 145 extending from a portion of the stable pads 141.
Also, in a center of each of the stable pads 141, an insertion hole (not shown) is formed which receives an insertion protrusion 146 therethrough.
In the subordinate driving shaft link unit 140, the hook protrusion 144 is hooked on the other end portion 152 of the spring 150, and the limit protrusion 145 is inserted into the other arc opening 121 formed in the base plate 120 to limit the rotation of the subordinate driving shaft link unit 140.
The link 143 includes insertion openings 143a formed in each end portion thereof. The insertion protrusion 146 of the stable pads 141 and an insertion protrusion 163 extending from a portion of the central shaft unit 160 are correspondingly inserted into the respective insertion openings 143a, whereby the rotation force of the subordinate driving shaft link unit 140 is transferred to the central shaft unit 160.
The central shaft unit 160, as shown in FIG. 2, includes a central shaft 162, and a stable arm 161 having an insertion protrusion 163. The central shaft 162 extends from another end portion of the unit 160.
The operational steps of a conventional two-position switching actuator for a load switch according to the manual control method will now be described with reference to the accompanying drawings.
As shown in FIGS. 2, 3 and 6-8, when the control handle 110 is gradually rotated in the clockwise direction, the rotational force of the control handle 110 is transferred to the driving shaft unit 130 through the driving shaft 132 connected thereto. As a result, driving shaft unit 130 gradually rotates in the clockwise direction.
When the driving shaft unit 130 rotates in the clockwise direction, the hook protrusion 134 formed at the end portion of the driving shaft unit 130 rotates gradually in the clockwise rotation, thereby causing tension at the spring 150 hooked on the hook protrusion 134 (FIG. 7).
When the limit protrusion 133 of the driving shaft unit 130 reaches an end portion of one arc opening 121 of the base plate 120 after the continuous rotation of the driving shaft unit 130, the hook protrusion 144 extending from the end portion of the rear surface of the suborinate driving shaft link unit 140 instantly makes a counter-clockwise rotation in accordance with the elastic restoration force of the spring 150 (FIG. 8), whereby the subordinate driving shaft unit 140 rotates counter-clockwise.
When the subordinate driving shaft link unit 140 rotates in the counter-clockwise direction, the central shaft 162 connected to the link 143 makes a counter-clockwise rotation, thereby switching a contact position.
However, although such a two-position (open-close) switch operation may be completely carried out using the conventional switching actuator, more than two switching actuators are needed in order to perform other switching operations, such as a 3-position (open-close-earth) or a 4-position (open-close-open-close) contact switching operation.
Consequently, the conventional two-position contact switching actuator is inconvenient to use and the applicability of the conventional switching actuator is limited.
In addition, since an operator has to directly operate the load switch to control the conventional switching actuator, the conventional switch operation is time consuming and dangerous to the operator.